1. Field of the Invention
The present invention relates to a fan wheel structure for a blower fan. In particular, the present invention relates to a fan wheel structure for a blower fan that drives air to flow in an improved, smoother manner.
2. Description of the Related Art
FIG. 1 of the drawings illustrates a conventional blower fan comprising a casing 90 having an axle tube 91 around which a stator 92 is mounted. A bearing 93 is mounted in the axle tube 91 for rotatably holding a central shaft 95 of a fan wheel 94. The fan wheel 94 comprises an annular wall 98 and an annular plate 96 extending radially outward from a bottom edge of the annular wall 98. Plural blades 97 are mounted upright on an annular outer edge of the annular plate 96 and spaced from the annular wall 98 by an appropriate gap. When the fan wheel 94 is driven to turn, air is sucked into the blower fan an exits via an outlet by the blades 97. Such a conventional blower fan creates a suction force for driving the air by means of a turbulent flow passing through a swirl passage in the casing 90. Therefore, the blowing effect largely depends on the smoothness of the flow. However, the joint area between the annular wall 98 and the annular plate 96 is at a right angle such that the sucked air would accumulate in the joint area and thus form turbulence.
Taiwan Utility Model Publication No. 388203, issued to Applicant on Apr. 21, 2000 and entitled AN WHEEL STRUCTURE as illustrated in FIG. 2 of the accompanying drawings of the present application, discloses a fan wheel 80 comprising plural axial flow blades 82 and plural blower blades 83 on an outer periphery of an annular wall 81 thereof. When the annular wall 82 turns, the axial flow blades 82 drives air along an axial direction while the blower blades 83 drives air along a direction orthogonal to the axial direction.
It is the primary object of the present invention to provide a fan wheel structure for a blower fan that drives air to flow in an improved, smoother manner, thereby providing an improved blowing effect.
The fan wheel structure in accordance with the present invention comprises an annular wall, a central shaft extending along a central axis of the annular wall, an annular bottom plate extending outward from a bottom of the annular wall, and plural blades provided on the bottom plate. A joint area between the annular wall and the annular bottom plate is an annular arcuate wall to avoid interference with the air driven by the fan wheel, thereby providing a smoother airflow.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.